Influence Of Density Variation Research Articles

Numerical Analysis Related to the ROCOM Pressurized Thermal Shock Benchmark

The development, verification, and validation of Computational Fluid Dynamics (CFD) codes in reference to nuclear power plant (NPP) safety has been a focus of many research organizations over the last few decades. Therefore, a collection of Rossendorf Coolant Mixing Test Facility (ROCOM) CFD-grade experiments was made obtainable to line up a global International Atomic Energy Agency (IAEA) benchmark regarding Pressurized Thermal Shock (PTS) situations. The benchmark experiment describes the complicated flow structures in mixed convection zones of the RPV during PTS events. The experiments were utilized to validate CFD codes. Additionally, an experiment with no buoyancy forces was elite to point out the influence of density variations. Compared to earlier studies, the turbulence models of the CFD code improved a lot. The turbulence modeling approach shows a respectable agreement with the experimental data.

Influence of density change on the detection of breast liposarcoma by magneto-acousto-electrical tomography

Magneto-Acousto-Electrical Tomography (MAET) has the advantage of high spatial resolution and high image contrast and is expected to achieve early breast cancer diagnosis. At present, the density of biological tissue is usually assumed to be the density of water. The effect of density changes on the MAET signal has not been studied. Liposarcoma of the breast is a common malignant tumor. Unlike normal breast cancer which occurs in the gland, liposarcoma of the breast occurs in the fat of the breast. However, the fat density of the breast is widely distributed, which is different from that of liposarcoma. Therefore, it is very important to study the effect of density change on the MAET signals. In this paper, a finite element simulation model is established to consider the influence of density variation on the MAET signal. The simulation results show that an increase in density reduces the amplitude of the original MAET signal. The degree of reduction in signal amplitude is proportional to the increase in signal density. The simulation results are consistent with the theoretical analysis. Finally, the MAET experimental platform is built to validate the simulation results of MAET signals. The simulation and experiment results show that the change of density greatly influences the detection of breast liposarcoma based on MAET. It cannot be directly equivalent to the density of water. The results of this study indicate that MAET is expected to detect the early diagnosis of breast liposarcoma.

Experimental Study of the Mechanical Behavior of Local Wood Terminalia Superba (Fraké) by Glued Wood Assembly According to the Beveled Configuration

The design of structural elements, the design of connections and supports, and damage have a significant influence on the technical characteristics of wood construction projects. An innovative experimental study was carried on locally obtained glulam beams. This study aimed to evaluate the load-bearing capacity of a finger-jointed Terminalia Superba (fraké) lamellae during routine use of an adhesive in the local area and to improve the connections in glulam structures. The achievement of this objective will allow to determine the influence of the technical characteristics of finger-jointing on the mechanical resistance, to maximize the mechanical resistance of the reconstituted beams, and eventually to minimize the losses due to sawing. All this will have a considerable impact on the technical and economic aspects of a wood construction project. The physical aspect of the species was studied and properties found. The influence of variation in density, the bonding surface, and joint efficiency on the bending strength (MOR) of Terminalia Superba (fraké) was studied. Mechanical properties were found and related to the optimum joint angle α, and the breaking point reads 0.20 mm. For the angular range of [0°–30°], adhesive failures are witnessed, and beyond this range, the failures are mixed. The 45° finger-jointing angle appeared to be better in the axial traction mode of rupture.

The bond strength development of coconut wood in relation to its density variations

ABSTRACT This study examines the influence of density variations in coconut palm wood (Cocos nucifera L.) on bond strength development using three types of adhesives: urea formaldehyde (UF), melamine urea formaldehyde (MUF), and polyvinyl-acetate (PVAc). A special testing device called Automated Bonding Evaluation System (ABES) was used to investigate the bond strength development between coconut veneers as a function of adhesive type, wood density (moisture content of 10%), pressing time, and bond-temperature development. Coconut wood density was shown to greatly affect the bond line. The bond strength of medium-density material (600–700 kg/m3) was lower than that of high-density material (900–1,000 kg/m3). Interestingly, the medium-density coconut veneers achieved higher bond strength with shorter pressing times, while the high-density coconut veneers reached better results with longer pressing times. Moreover, the bond strength improved by increasing the hot-pressing time resulting in higher bond-line temperatures. A comparison was made between coconut wood and beech wood for similar bonding parameters.

Bending properties of finger-jointed Malaysian dark red meranti

ABSTRACTThe mechanical performance of dark red meranti (Shorea spp.) containing structural finger joints was investigated in four-point bending. The influence of variation in density on the bending strength (MOR) and stiffness (MOE) of dark red meranti (DRM) was studied. The effect on these properties of variation in end pressure when bonding was examined. The orientation of finger joints and the effect of cross-sectional area of bonded joints on the bending properties were also investigated.The results of this study indicate a positive relationship between the density and the MOR of DRM specimens. Sufficiently high end pressure is needed to produce strong finger joints. The orientation of finger joints and the changes in cross-sectional area of bonded joints showed no influence on the MOR. The MOE of DRM was not affected by the finger jointing of the pieces. In conclusion, finger-jointed DRM exhibits potential for structural uses, particularly for glulam beams.

Transient Analysis of Contaminant Diffusion in the Wellbore of Shale Gas Horizontal Wells

This study focuses on the transient analysis of diffusion of a contaminant ejected by an external source into a laminar flow of recovered water. The influence of density variation with contaminant concentration is approximated according to the Boussinesq approximation. On the basis of momentum conservation and mass conservation theory, recovered water flow and mass transfer partial differential equations (PDEs) describing contaminant diffusion are obtained. This problem under three kinds of boundary conditions is solved analytically using Laplace transform method. By comparing the actual measured concentration in horizontal well of X shale gas reservoir and the concentration obtained from the models, the type of boundary conditions of X shale gas reservoir is determined. After that, sensitivity analysis of the influence of each parameter on the concentration of contaminant is presented. The determination of boundary condition type can determine the fracture form, which provides the basis for the flow and diffusion of the fluid in the fracture. The model also can be quite useful for available necessary early warning methods for detecting or predicting contaminant concentration and hence help mitigate related environmental pollution by earlier instituting relevant decontamination measures.

Influence of density variation on the arbitrarily propagating crack tip fields in functionally graded materials

The stress and displacement fields for an arbitrarily propagating crack tip in functionally graded materials (FGMs) with exponential variation of density and shear modulus are obtained. Nonhomogeneous parameters of density and shear modulus are different from each other. The solutions for higher order terms in the dynamic equilibriums are obtained by transforming the general differential equations to the scaled Laplace’s equations. Using the stress fields, the effects of the nonhomogeneous density on stress components is investigated. In addition, the contours of the constant maximum shear stress at a propagating crack tip are generated and the effects of the nonhomogeneous density on the isochromatics are discussed.

Viscoelastic modeling of the diffusion of polymeric pollutants injected into a pipe flow

This study focuses on the transient analysis of nonlinear dispersion of a polymeric pollutant ejected by an external source into a laminar pipe flow of a Newtonian liquid under axi-symmetric conditions. The influence of density variation with pollutant concentration is approximated according to the Boussinesq approximation and the nonlinear governing equations of momentum, pollutant concentration are obtained together with and Oldroyd-B constitutive model for the polymer stress. The problem is solved numerically using a semi-implicit finite difference method. Solutions are presented in graphical form for various parameter values and given in terms of fluid velocity, pollutant concentration, polymer stress components, skin friction and wall mass transfer rate. The model can be a useful tool in understanding the dynamics of industrial pollution situations arising from improper discharge of hydrocarbon pollutants into, say, water bodies. The model can also be quite useful for available necessary early warning methods for detecting or predicting the scale of pollution and hence help mitigate related damage downstream by earlier instituting relevant decontamination measures.

밀도변화가 직교이방성함수구배재료에서 전파하는 모드 III 균열선단의 응력 및 변위장에 미치는 영향

The influences of density variation on stress and displacement fields at a propagating Mode-III crack tip in orthotropic functionally graded materials (OFGMs) are studied. The crack propagates dynamically at a right angle to the gradient of physical properties. Three kinds of elasticity and density gradients are analyzed in this study. They are as follows: (1) the density varies without elasticity variation, (2) the directions of the density and elasticity gradients are opposite to each other, and (3) same. For these cases, the stress and displacement fields at the crack tip are developed and the dynamic stress intensity factors for propagating cracks are also studied. When the crack speed is low, the influence of density variation on the stresses and displacement is low. However, when the crack speed is high, this influence is very high.

Influence of Density Variation on One-Dimensional Modeling of Exhaust Assisted Catalytic Fuel Reforming

Exhaust gas recirculation has become commonplace within the automobile industry to reduce nitrogen oxide emissions because of its ability to lower the combustion temperature. However, it leads to an increase of particulate matter and degradation in fuel economy. One possible avenue for recovering this efficiency is to use exhaust assisted fuel reforming (EAFR) to generate hydrogen by catalytic means using injected fuel and exhaust and add it to the inlet mixture. Adding hydrogen in this manner has shown an increase in combustion stability and efficiency of the engine while reducing particulate matter production. Many classical works use incompressible fluid flow models in order to simulate the reactive flow in monolithic catalyst. However, such models are not appropriate in the case of EAFR, where exothermic reactions cause a large increase in the temperature and consequently in density. To simulate a catalyst undergoing EAFR reactions, a compressible flow solver was used in order to take into account the changes in density. The presented results show the importance of using proper gas dynamics and heat transfer for modeling a flow with catalytic reactions of high exothermicity.

Analysis of Nonlinear Dispersion of a Pollutant Ejected by an External Source into a Channel Flow

This paper focuses on the transient analysis of nonlinear dispersion of a pollutant ejected by an external source into a laminar flow of an incompressible fluid in a channel. The influence of density variation with pollutant concentration is approximated according to the Boussinesq approximation, and the nonlinear governing equations of momentum and pollutant concentration are obtained. The problem is solved numerically using a semi‐implicit finite difference method. Solutions are presented in graphical form and given in terms of fluid velocity, pollutant concentration, skin friction, and wall mass transfer rate for various parametric values. The model can be a useful tool for understanding the polluting situations of an improper discharge incident and evaluating the effects of decontaminating measures for the water body.

Transient double-diffusive convection in an enclosure with large density variations

An extension of a slightly compressible flow model to double-diffusive convection of binary mixtures of ideal gases enclosed in a cavity is presented. The problem formulation is based on a low-Mach number approximation and the impermeable surface assumption is not invoked. The main objectives of this work are the statement of the mathematical model used, and the analysis of some significant results showing the influence of density variation on transient solutions for pure thermal or pure solutal convection as well as for thermosolutal convection in the special case where the thermal and solutal buoyancy forces are equal in intensity either for aiding or for opposing cases.

Effects of the density perturbation in scattering

[1] The influence of density variation on scattering is investigated in terms of attenuation, coda level, and apparent frequency shift. The influence of density variations is to produce more scattered energy than for velocity perturbations alone with a consequently higher coda level. The temporal decay of the coda is reduced, so that high perturbations in density are associated with a long duration of coda. These effects are particularly important for media with small-scale heterogeneity. Thus inversions for heterogeneity parameters, based on the character of precursors and coda of seismic phases penetrating deep into the Earth, need to take into account the nature of the density variations as well as wave speed variations.

Optimization of a Violin Top with a Combined Laminate Theory and Honeycomb Model of Wood

Summary Stochastic optimization with the simulated annealing method (SA) is performed on a violin top made of Norway spruce (Picea Abies). A numerical example is presented which shows that it is possible, through changes in thickness variables, to compensate for changes in vibration properties caused by a variation in the material parameters in the top. A material model is also presented for the blank which considers the influence of density variations in the annual rings, the cellular structure of wood and reinforcement from the wood rays.

Influence of density variations on the structure of low-speed turbulent flows: a report on Euromech 237

The European Mechanics Colloquium number 237 was held at the Institut de Mécanique Statistique de la Turbulence (Université d'Aix-Marseille II) from 18 to 21 July 1988. This was the first meeting to consider the influence of density variations on turbulent flows for both non-reacting and reacting flows in a variety of configurations. Several new experiments, computational models and theoretical analyses were presented for non-reacting flows. All these approaches showed the marked effects of density variations on coherent structures in turbulent shear flows. It was found that the approximate models used for turbulent Reynolds stresses in homogeneous flows do not need to be changed for the mean flow field but predictions for variances and correlations are still rather uncertain: in fact experimental results providing such information in variable-density flows are rare. The special problem of measuring turbulence in flows with density variations was discussed. In the discussions it was agreed that there are in fact strong similarities in the effects of density gradients on the dynamics of non-reacting flows and reacting flows despite the differences in the distributions of density gradients. Participants at the meeting from industry emphasized the importance of these flows to many different kinds of industrial and environmental problems.

Influence of density variation on the stability of a vortex with a top-hat jet core

The stability of a potential vortex with an injected rotating and nonrotating jet core is considered for different density ratios of the vortex to the jet. Growth rates are given for different ratios of the vortex strength to the axial jet velocity. It is shown that the vortex is less unstable as the density ratio increases.